As mentioned before, Firefox 3 is becoming available for those who are running -current, not users of -release or -stable. If you are unfamiliar with these terms, you should study Section 5.1 of the FAQ:

Correct. Firefox 3 is not available to users of 4.3-release. Most likely, it will not be backported.

The link provided in your original message is to the -current ports tree. The -current ports tree is only to be used with the -current system. Those who attempt to mix -current packages & ports with -release or -stable will at best experience weird behaviour; at worst, the applications will not function at all. For more information, study Section 15.4.1 of the FAQ: